Kicad Electronics design¶

KiCad is an open source, cross-platform Electronics design program. It can be found in the official-kicad-website.

During Fabacademy, we will be using the FAB library, adapted for SMD (or surface mount devices). You can find the libraries, adapted for Kicad V5.0 here. Also, some extra repositories to have around:

Symbols:

https://github.com/KiCad/kicad-symbols

git clone git@github.com:KiCad/kicad-symbols.git

Footprints:

https://github.com/KiCad/kicad-footprints

git clone git@github.com:KiCad/kicad-footprints.git

Understanding Kicad¶

Kicad is a set of different tools that are used for:

• Create schematics with Eeschema
• Create PCB layouts with Pcbnew
• Generate and see Gerber files with Gerber Viewer

The workflow goes like:

• Import libraries into Kicad (only to be done once)
• Create the schematics with Eeschema
• Create a Netlist
• Import the Netlist into the Pcbnew editor
• Create the PCB layout
• Export into SVG
• Edit the file into a vector editing program (Inkscape or similar)
• Machine it
• Solder it

You can see an overview of the hole workflow below:

Import libraries¶

First, we have to include the fab library - fab.lib, specifically for Kicad. For this, we will:

1. Click on the Schematic Library Editor icon (second icon):
2. Click on Preferences > Manage Symbol Libraries. There, we select the fab.lib library we have just downloaded:
3. Close the Schematic Library Editor. Now, open the Footprint Library Editor:
4. Click on Preferences > Manage Footprint Libraries:
5. Close the Footprint Library Editor. We are all set!

Create an schematic¶

Now, we can launch the Eeschema - Electronic schematic editor and begin with the schematics design. In order to add components, we will click on the Place component icon and selecting the elements needed from either the fab library we have included or other custom libraries of our own.

In the schematic we basically want to place components and connect them with wires. As simple as that. Once we have finished with the schematics design, having assigned all the names, values and footprints to the components, we should click on Generate Netlist, which is a list of components and references which serves as a link between the schema and the PCB layout editor:

This will create a .net file that we will be import later into the Pcbnew editor.

PCB-design¶

We can now close the Eeschema editor and open PCBnew. First thing is to load the Netlist by clicking on Read netlist. We can keep normal settings and click on Read Current Netlist. One should carefully read the Messages area in case of any error (normally in red) and review the schematic in Eeschema in case of errors.

Now, it is time to set the design rules. For this, click on Setup > Design rules…>. We see two tabs, the Net Classes Editor and the Global Design Rules. The latter applies to all the design, and we will use a minimum track width of 0.4mm, leaving the rest to default (since we are not placing vias). In the Net Classes, we can specify classes for each Net. For example, we would maybe want to specify different rules for the power signals and the I2C protocol ones. We can do so in this tab. We will be using the same width for all the tracks, and for this we will edit the Default profile. If we wanted, we could add more, and generate for example a different one for power (see the example below).

The set of rules to be used are shown below, which comply with the tools we’ll be using for the tracks (1/64”). Sometimes, you can use 0.2 for the clearance, if you want to pass between the pads of the ISP header, for instance:

Note that when setting these design rules, the dropdown at the top should change to the stablished rule:

Now it’s time to do the routing. At the begining, all the components are disconected (only with white lines) and all on a pile. With the help of the M key we can arrange them quickly and comence with the routing. We can add tracks between the pads by clicking on Place trace and selecting the pads. The tracks and pads are added in the F.Cu layer, while the cuts are done in the Edge.Cuts layer. We can draw the cuts using the Add graphic line or polygon tool.

Cut-out¶

The PCB cut-out is done in the Edge.Cuts layer. In this layer, we will use the Add Graphic Lines tool:

Here, it’s interesting to have the cross-hair cursor (6th button on the left pannel) to help us drawing.

Export¶

Once we have it routed, it’s time to go for the fabrication. There are several ways to export, and the common way of doing so if the PCB was to be manufactured outside of a Fablab, would be to Generate the gerber files. In our case, we will export an SVG file, that we can later on import in Fabmodules, or generate a PNG.

If you want to export it to SVG and then use a vector program to edit it (Inkscape, or Illustrator), click on File > Export SVG with the following configuration:

Pay attention that we will save all of the layers into the same file, because we will be editing the SVG in a vector program.

Traces file creation¶

Now, in a program where we can edit vectors, such as Illustrator or Inkscape, we will generate the PNG file that will go into fabmodules or mods. We will:

• Import the SVG file
• Arrange the layers into Traces and Cut
• Export each layer separately into pngs:

First, we import the SVG file and we arange the components into layers:

For this: 1. We select Layer > Layers… and add Traces and Cut. 2. Then, we select the traces components and move them to the Traces layer. We hide this layer. 3. We select the cuts and put them in Cut 4. We fill the object with the paint bucket in white 5. We add a rectangle, with black fill that covers the hole cuts area and move it to the background 6. We activate show the traces layer 7. Select everything and move it to (0,0)

Once we have done all this, we can export each layer to a PNG. Take care of the position of the export (X0, Y0 and X1, Y1 or width / height) to match the actual size. In here, the background rectangle from step 5 is useful:

And we are done! Now we can send to the milling machine!

Class example¶

Here are some screenshots of what the schematic we did in class:

Slider Switch Area

FTDI Area

Reset Switch Area